Hydraulic leveling device



Nov. 20, 1956 s. A. HOOKER HYDRAULIC LEVELING DEVICE v F1led .Nov. ,2, 1954 2 Sheets-Sheet 1 If G: j

ATTORNEYS.

Nov. 20, 1956 s. A. HOOKER 2,770,914

HYDRAULIC LEVELING mzvxcs:

Filed Nov. 2. 1954 2 Sheets-Sheet 2 INVENTOR. 5a ma i 44.1%]?67} QBMQJ A TTORNEYS HYDRAULIC LEVELING DEVICE Samuel Arthur Hooker, Martinsville, Va.

Application November 2, 1954, Serial No. 466,341 r 3 Claims. (Cl. 45- 86) This invention relates to a hydraulic leveling device and more specifically concerns a book stand having a novel leveling means incorporated therein.

Self-leveling book stands have been manufactured and sold in substantial quantities, as they are particularly adaptable for holding relatively thick and heavy books such as encyclopedias, unabridged dictionaries and the like. It has been recognized that, when a thick book is placed on a level surface and opened the pages are not flat. This makes the reading surface difficult to read. Accordingly it has been highly advantageous to provide a structure whereby the pages are flat wherever the book may be opened. One heavy duty book stand which has met with considerable success has been manufactured and sold under U. S. Patents Nos. 2,260,694 and 2,260,- 695.

It is an object of this invention to provide a book stand which embodies structural and functional advantages over the book stands of the aforementioned patents. Still another object of this invention is to provide a novel and highly efiicient hydraulic leveling mechanism. Other objects and advantages of this invention will appear in further detail hereinafter and in the drawings whereof:

Fig. 1 represents a view in perspective illustrating a book stand embodying features of this invention; and

Fig. 2 represents a vertical elevation of the hydraulic leveling mechanism of the book stand, portions of the hydraulic leveling mechanism being broken away and shown in section in order more particularly to illustrate important details.

Turning now to the specific embodiment of the invention selected for illustration in the drawings, the number designates a base to which a vertical post 11 is secured. Fixed on top of the post 11 is a cross brace 12 which extends upwardly at an acute angle to the vertical. A U-tube 13 has a pair of parallel spaced apart legs 14 the upper ends of which extend through the cross brace 12 and are affixed thereto. Telescopically received in the upper ends of legs 14 are a pair of piston members 15 having tables 16 fixed to their upper ends. Guide rods 17 are fixed to the table 16 and extend downwardly parallel to the legs 14 through guide openings formed in the cross brace 12. Adjustable plates 20 are mounted on the tables 16 to support the covers of a book 21.

Turning now to Fig. 2 of the drawings, it will be appreciated that the legs 14 are hollow tubes, and that the U-tube 13 includes a hollow base 22 which communicates with both legs 14. Hydraulic fluid F is disposed in the legs 14 and in the base 22.

Piston members 15 are also hollow tubes. At their upper ends they are seal welded to the plate 16. Air bleed screws 23 are threaded through the piston members 15 adjacent their upper ends. Depending from the lower ends of piston members 15 are pistons 24 which may consist of leather, rubber or the like. Pistons 24 have metal back-up plates 25 which are fixed to the piston members 15 by rigid straps 26. Each tube 15 is provided with a vent 27 for the trapped oil.

The normal oil level inside the piston member .15 is indicated by ,the letter L. The space inside the member 15, above the level L, is filled with air or some other readily compressible fluid. The number 30 designates a conventional seal between theU-tube leg 14 and the piston 15. r A r A stop brace 31 is welded or otherwise affixed to the bottom of each leg 14 at its intersection with the base 22. The stop brace 31. is preferably an angle iron having arms at right angles to one another. A helical spring 32 extends axially along each leg 14 between the stop brace 31 andthe lower face of piston 24. Spring 32-is normally under compression. 1 I r From the foregoing description the operation of the hydraulic leveling mechanism will be apparent. Referring to Fig. 2 for example, the opposed springs 32 are each acting upwardly upon the pistons 15, thereby counterbalancing the weight of the book or other object supported by the tables 16. When an unbalanced force is exerted downwardly on the left hand table 16 as viewed in Fig. 2, the force is resisted by spring 32, which yields downwardly and is further compressed. With the movement of piston 24 downwardly hydraulic fluid is pumped out of the left hand leg 14 into the righthand leg 14, thereby tending to raise the right hand table 16. In fact, the right hand table 16 will be raised to substantially the same extent as the left hand table 16 is lowered.

As the left hand table 16 moves downwardly, the corresponding spring 32 exerts a continuously increasing force. Concurrently, with the movement of right hand table 16 upwardly, its spring is longitudinally extended, and exerts a continuously decreasing upwardly directed force. Eventually the downwardly exerted unbalanced forces are equalized or balanced by the unbalanced upwardly directed forces exerted by the springs, and the relative movement of the tables stops. In the resulting static condition, oil from the right hand leg 14 tends to leak back to the left hand leg 14, seeking its own level. As the oil leaks past the piston oil seals 24 its flow is cushioned and resisted by the compression of the air trapped in the upper portion of the left hand piston member 15. It will be appreciated that the extent of such cushioning action may be varied by providing various means permitting fluid leakage past the piston oil seals 24, such as slots, for example. It will be appreciated that, when the air in left hand piston member 15 is compressed the air in right hand piston member 15 is expanded, thereby providing further cushioning action. As a result of the coaction of the various members embodied in the legs 14, a positive yet smooth and cushioned movement of the tables 16 is obtained.

The automatic leveling device of this invention has utility in connection with bookstands and with other types as well. In fact, it is not inconceivable that it has utility in automobiles, trunks, etc. and in balancing floors, platforms and the like.

It will be appreciated that the device may be modified in a variety of other ways. For example, equivalent mechanisms may be substituted for those shown in the drawings provided they function in a similar manner to accomplish a similar result, parts may be reversed, and certain features of the invention may be used independently of other features, all within the sipirit and scope of the invention as defined in the appended claims.

Having thus described my invention, I claim:

1. A hydraulic leveling device comprising a base, a pair of hollow legs extending upwardly from said base, said legs containing a hydraulic fluid, a pair of pistons extending telescopically into the tops of said legs, said pistons being hollow providing spaces therein, said spaces containing a compressible fluid, platforms fixed on top of the pistons, hydraulic means connecting said legs to Patented Nov. 20,1956

one another below said pistons, and compression springs anchored adjacent the bottoms of said legs extending upwardly inside said legs bearing on the bottoms of said pistons, whereby a movement of one platform in a predetermined direction causes a corresponding movement of, the other platform in the opposite direction.

2. A hydraulic leveling device comprising a hollow U-tube containing hydraulic fluid, hollow sleeves slidably reciprocable in the legs of the U-tube, tables sealing the tops of said sleeves, pistons on the bottoms of said sleeves in said fluid, and compression springs anchored adjacent the bottoms of the legs of the U extending upwardly in side said legs bearing on the bottoms of saidpistons.

3. A book stand comprising a support having legs, a hollow U-tube fixed to said legs extending upwardly from said support at an acute angle to the vertical, said U-tube having a pair of substantially parallel legs containing hydraulic fluid, piston members slidably reciprocable in structed to support a portion of a book, a cross brace extending between the legs of the U-tube, and guide means fixed to said platforms and extending through said cross brace.

References Cited in the file of this patent UNITED STATES PATENTS 1,433,162 Sweetland Oct. 24, 1922 2,552,941 Courtney May 15, 1951 FOREIGN PATENTS 147,367 Australia Feb. 23, 1950 

